This invention relates to high intensity mixing machines for elastomeric materials. A batch of ingredients including carbon black is fed into a hopper which has a ram weight connected to a piston rod for controlling movement of the materials into the mixer. The hopper is closed except when the ingredients are being loaded.
Internal mixers of a 8.36 cubic feet (237 liter) size such as a that shown in U.S. Pat. No. 5,492,403 have been made and operated in rubber plants for many years. The mixer body has had a rectangular throat opening of 11.5 inches (29.21 cm) by 32 inches (81.28 cm), a piston-cylinder with an 11 inch diameter (27.94 cm) for operation on 100 psi, (7.03 kg/sq cm), factory supplied air pressure providing an effective stock pressure of 27.2 psi (1.91 kg/sq cm). Mixing time, that is the time required to raise the temperature of the rubber mixture from ambient (room temperature) of 80xc2x0 F.-90xc2x0 F. (27xc2x0 C.-32xc2x0 C.) to a discharge temperature of 350xc2x0 F., (662xc2x0 C.) has been 3.5 to four minutes. Loading time has taken from one to several minutes.
The mixer body has been replaced approximately every seven years because of wear in the throat area and inside the mixer body. Complete replacement of these 237 liter mixers with new larger mixers has not been feasible in older rubber plants because of the increased weight of the new mixers which would require extensive changes to the rubber plant. Also the cost of new mixers and other equipment for the larger size mixer is substantial. [$2,200,000 for a new 8.36 cubic foot (270 liter) mixer assembly].
The present invention is directed to a modification of the present 8.36 cubic feet (237 liter) size internal mixer which does not require enlarging the size of the mixer body. By increasing the size of the throat of the mixer body, adding a new size ram weight and hopper and a new size piston-cylinder apparatus, substantial improvements in production and quality have been achieved. Also, by adding wear plates at the throat area, the time between replacements of the mixer body has been increased.
In accordance with one aspect of the invention there is provided: an internal mixer for mixing petrochemical materials and other ingredients to be vulcanized comprising a mixer body, a mixing chamber in the body, a throat opening for charging the mixer, a discharge opening for discharging the mixer, a ram weight, a hopper and a piston-cylinder assembly for urging the ram weight into the throat opening and applying pressure to the petrochemical materials and other ingredients in the mixing chamber characterized by the mixing chamber having a volume not over 8.36 cubic feet (237 liters), the throat opening having an area of at least 576 square inches (3,715 cm2), the hopper having a cross sectional area of at least 576 square inches and the ram having an area of at least 576 square inches (3,715 cm2).